1. Field of the Invention
This invention relates to a process for decomposing a pollutant using a microorganism, particularly a process for decomposing a halogenated organic compound using a microorganism which has an activity to decompose the halogenated organic compound, to a process for environment remediation, which can decompose a pollutant in the environment, such as ground water, soil and so on, and to a microorganism capable of decomposing a pollutant and being used in the decomposition and remediation processes.
2. Related Background Art
The by-products resulting from the disinfection process of city water have been a serious concern since the U.S. Environmental Protection Agency reported on them in the 1970s. In Japan also, where chlorination of city water is compulsory, the by-products such as trihalomethanes, halogenated acetic acids, halogenated acetonitriles and halogenated ketones have been detected in city water, and has become a great problem because of their liver toxicity and mutagenicity. Particularly halogenated organic acids, for example halogenated acetic acids such as chloroacetic acid, dichloroacetic acid, trichloroacetic acid and bromoacetic acid have been designated as environment surveillance items in Japan since 1993, attracting a great deal of attention as a new problem. Details are reported in "Analytical Methods for Revised Standards of Water Quality and Environment" in the Proceedings of the 23rd Seminar of Water Environment Society of Japan (Incorporated Association of Water Environment Society of Japan), November 1993, pp.55-64.
These halogenated organic acids cannot be degraded by aeration. As one of the countermeasures, for example, biodegradation treatment such as a bioreactor is very useful because treatment can be conducted under mild conditions and is relatively low in cost.
Microorganisms having a decomposing activity of halogenated organic acids have been studied, for example, molds such as Trichoderma, Acrostalagmus, Penicillium and Clonostachys, and bacteria such as Pseudomonas, Arthrobacter, Rhizobium, Agrobacterium, Bacillus, Alcaligenes, Nocardia, Micrococcus, Achromobacter and Moraxella (Protein, Nucleic Acid and Enzyme (1984), vol.29, p.101-110). Adachi reported that an unidentified strain OS-2 has an enzyme which can decompose chloroacetic acid, bromoacetic acid and iodoacetic acid to about the same extent, and OS-2 can also decompose dichloroacetic acid though to half the extent of the above compounds (Proceedings of Osaka Prefectural Institute of Public Health, "Public Health" No. 30, p.89 (1992)). Furthermore, decomposition of halogenated organic acids having two to six carbons was studied using dehalogenase extracted from Pseudomonas putida NCIMB 12018 and immobilized on carboxymethyl cellulose or thioglycolic acid. (European Patent No. 179603).
The relation between dehalogenating enzymes for decomposing halogenated organic acids and their genes has been studied using Pseudomonas putida AJ1 strain (J.Gen. Microbiol., 138, p.675 (1992)), Pseudomonas cepacia MBA4 strain (J.Biochem., 284, p.87 (1992)) and Pseudomonas sp. CBS3 strain (Biol. Chem. Hoppe-Seyler., 374, p.489 (1993)).
All these studies are done on the enzyme level, and not on the actual behavior of the microorganisms in the polluted waste water. Concerning the microbial decomposition of halogenated organic acids, only Xanthobacter autotrophicus GJ10 strain (Appl. Biochem. Biotechnol., 40, 158 and 40, 165 (1993)) has been studied.
Japanese Patent Laid-Open Application No. 4-64544, discloses dehalogenase extracted from Pseudomonas which decomposes D- and L-chloropropionic acid into lactic acid. This is, however, also a study at the enzyme level.